This invention relates to diorganopolysiloxane compositions and more particularly to compositions containing diorganopolysiloxanes and copolymers which are prepared in the presence of the diorganopolysiloxanes.
More specifically the invention relates to diorganopolysiloxane compositions containing copolymers which are derived from monomers consisting of at least ethylene and vinyl acetate and to a process for preparing the diorganopolysiloxane compositions.
Compositions containing diorganopolysiloxanes and a polymer which is prepared in the presence of the diorganopolysiloxanes have been known heretofore. For example, it has been known that monomers containing aliphatic unsaturation can be polymerized in the presence of diorganopolysiloxanes and free radical initiators. In U.S. Pat. No. 4,026,853 several patents are disclosed which describe the preparation of modified organopolysiloxanes by polymerizing monomers containing aliphatic unsaturation in the presence of organopolysiloxanes and free radical initiators. This patent also discloses a large number of monomers containing aliphatic unsaturation, including ethylene and vinyl acetate which may be employed in the polymerization. However, the preparation of ethylene and vinyl acetate copolymers in the presence of diorganopolysiloxanes has not been known heretofore.
Compositions prepared heretofore from the polymerization of monomers containing aliphatic unsaturation in the presence of diorganopolysiloxanes and free radical initiators have several disadvantages. For example, these compositions migrate on vertical or inclined surfaces and flow out of vertical fissures. In order to overcome these disadvantages, it was necessary to add fillers such as described in U.S. Pat. No. 3,580,971. Also, U.S. Pat. No. 3,776,875 discloses that polymerization compositions prepared in the presence of solvents are thixotropic and will not migrate on vertical surfaces. One of the disadvantages of adding fillers is that they may produce an undesirably high viscosity or lead to solidification of the compounds. In addition, incorporation of fillers into the compositions substantially increases the cost of the products. Likewise, compositions obtained from the polymerization of methacrylic acid in the presence of diorganopolysiloxanes must contain an undesirably high percentage of diorganopolysiloxane, otherwise they will have an undesirably high viscosity. Moreover, when a solvent is employed in the polymerization, the resultant products, when molded, have a tendency to shrink as the solvent evaporates. In contrast to the compositions described heretofore, the compositions of this invention exhibit non-slump properties in the absence of fillers or polymethacrylic acids. Moreover, it is no longer essential that the compositions be prepared in the presence of solvents in order to obtain the desired non-slump properties. Likewise, these compositions are non-slump in the absence of other materials, except crosslinking agents.
Therefore, it is an object of this invention to provide organopolysiloxane compositions. Another object of this invention is to provide compositions containing diorganopolysiloxanes and copolymers derived from monomers consisting of at least ethylene and vinyl acetate. Still another object of this invention is to provide compositions in which the copolymers are bonded to and/or dispersed in the diorganopolysiloxane. A further object of this invention is to provide organopolysiloxane compositions which will not migrate on the surface even in the absence of fillers. A still further object of this invention is to provide a process for preparing diorganopolysiloxane compositions having copolymers bonded to and/or dispersed in the diorganopolysiloxanes in which the copolymers derived from monomers consisting of at least ethylene and vinyl acetate are prepared in the presence of diorganopolysiloxanes and free radical initiators.